1. Field of the Invention
This invention relates generally to tube bending apparatus and methods, and more particularly to a tube bending apparatus having an elongate frame with lateral rollers on an upper surface and a feeding carriage and reciprocating ram disposed beneath the upper surface that moves a reversible bending die and backup tool along the upper surface relative to the lateral rollers, which provides a substantially unobstructed bending plane and allows very close successive bends to be made in the workpiece including transition bends and bends very close to a flared fitting and nut.
2. Brief Description of the Prior Art
Apparatus for bending pipes, tubes, and rods, generally comprise an elongate frame having a power means such as a drive screw or hydraulic ram mounted lengthwise on the frame with a curved forming die or bending shoe mounted on the end of the piston rod and a pair of cylindrical stop members or rollers secured on the frame transverse to the longitudinal axis of the power means. The tubular workpiece is held against the stops or rollers and the power means pushes against the center portion of the workpiece between the stops or rollers to form a bend in the workpiece.
Many conventional bending machines place the pushing apparatus in the bending plane of the workpiece which makes it difficult or impossible to bend a workpiece adjacent an already bent section, because the end of the previously bent section tends to strike the frame or the pushing apparatus. Another problem with conventional pipe bending apparatus is that the diameter of the pipe, tubing, or rod may be in inches or may be metric, in which case, the user would have to calculate the spacing of the stops or rollers and reposition different diameter rollers and bending shoe die members to accommodate the diameter of the respective workpiece.
Another common problem with conventional roller members and a curved forming die is that it is extremely difficult to form a bend very close to the end of a section of tubing which has a sleeved flared fitting and nut because the nut will not fit closely against the curved surfaces of the rollers and the forming die. In other words, the nut must be positioned outwardly beyond the radius of the curved surface of the rollers or forming die. Another problem commonly encountered with hydraulically powered bending machines, is that with many workpiece materials there is a tendency for the bent tubing or rod to "springback" after the hydraulic pressure is released, resulting in less accuracy of the finished bend angle.
There are several patents which disclose various apparatus for bending pipes, tubes, and rods which have a power means mounted lengthwise on a frame and utilize a curved forming die or bending shoe to push against the center portion of the workpiece between stops or rollers to form a bend in the workpiece.
Owens, U.S. Pat. No. 5,237,847 discloses a tube bending apparatus having a specially designed bending shoe which is configured to prevent crimping on small tubes during bending. The apparatus includes frame with a pair of angular slots on each side of the longitudinal axis of the power means and a pair of lateral rollers adjustably mounted in the slots. The rollers have a circumferential channel which is semi-circular in vertical cross section defining radial lips at the top and bottom of the channel. The specially designed bending shoe is a generally U-shaped member having a peripheral channel, semi-circular in vertical cross section, with a curved center portion and a pair of parallel lateral side portions having lips at the top and bottom of the peripheral channel. The lips on the lateral side portions of the bending shoe meet the lips on the lateral rollers to form a circle around the workpiece, but the lips of the curved center portion of the bending shoe extend beyond the center of the workpiece to prevent vertical expansion of the side wall of the tubular workpiece during a bend.
Schwarze, U.S. Pat. No. 4,788,845 discloses a pipe bending machine having a rotatable bending head at one end of the frame that has a plurality of vertical spaced bending grooves. A clamping jaw pivotally mounted on a longitudinally movable carriage slides angularly upward to clamp the pipe between the pivotal jaw and a selected bending groove of the bending head.
Sterghos, U.S. Pat. No. 4,788,847 discloses a rod bending machine having a longitudinally movable bending die which passes between a pair of lateral roller dies mounted on laterally spaced arms pivotally attached to the top of the frame wherein the movement of the bending die simultaneously effects movement of the two arms which support the lateral roller dies to bend the rod positioned between the bending die and lateral rollers.
Whitehead, U.S. Pat. No. 3,918,286 discloses a U-bolt bending machine having a longitudinally movable bending die which passes between a pair of roller dies mounted on laterally spaced arms pivotally attached to the top of the frame wherein the lateral spacing of the roller dies are adjusted by means of a threaded rod which extends transversely between the pivoting arms across the top of the frame.
Ware, U.S. Pat. No. 3,908,425; Goldberg, U.S. Pat. No. 4,005,593; Kelly, U.S. Pat. No. 4,254,651: Grimaldo, U.S. Pat. No. 4,833,907; and McMaster, U.S. Pat. No. 4,265,106 disclose various tube or pipe bending machines having a longitudinally movable bending die which bends the pipe or tube between stop members wherein the pushing apparatus lies in the same plane as the bending plane of the workpiece which makes it difficult or impossible to bend a workpiece adjacent an already bent section.
The present invention is distinguished over the prior art in general, and these patents in particular by a tube bending apparatus which has an elongate frame with a longitudinal slot in an upper surface thereof and removal rollers laterally spaced at each side of the slot above the upper surface. A rolling carriage and reciprocating ram are disposed beneath the upper surface. A vertical post secured to the carriage has an upper end extending through the slot and a reversible bending die is removably mounted on the upper end of the post above the upper surface of the frame. The bending die is advanced and retracted relative to the lateral rollers by the ram such that a section of a tubular workpiece held against said lateral rollers can be engaged by the bending die and bent into a curved configuration. The lateral rollers and bending die above the upper surface and the reciprocating axis beneath the upper surface provide a substantially unobstructed area around the rollers and bending die through which at least one free end of the workpiece may pass when being bent whereby a plurality of adjacent bends lying in the same plane or different planes may be made without a previously bent section striking the rollers, bending die, or ram. The bending die has a peripheral opening to receive a previously bent section for making transition bends, and in combination with a backup tool receives the nut and sleeve of a flared fitting for making bends very close to a flared fitting. An indicator disk may be installed on one roller to indicate springback.